During compression, refrigerating machines produce hot gaseous refrigerants which are generally called hot gas refrigerants. In the condenser which is connected at the output side this refrigerant discharges a large part of its heat to the atmospheric air or to cooling water and thereby becomes liquid. It is expanded in an evaporator through expansion valves and thereby absorbs heat from an area which is to be cooled whereby it again becomes gaseous. This heating and cooling effect is utilized for example in air-conditioning systems wherein the condenser and evaporator are interchangeable in their function and either heat or cool on the same outer side.
Ice which stems from the dampness of the surrounding air deposited in the evaporator on the ribs or in the pipes. In order to remove the ice and heat up the components again hot-gas refrigerant is supplied to the iced-up components for a certain time inside the refrigerating cycle. The normal operating process is thereby interrupted. The refrigerant is then drawn in from the compressor and only then is ready again for renewed use as a refrigerant. The hot-gas refrigerant can also serve to regulate the pressure on the operating side of the unit whereby use is made of the fact that in the case of gases a change in temperature is also always associated with a corresponding change in pressure.
Heating up or mixing is solely undertaken within the standard cycle by changing over to other components or by redirection.
The problems described above occur to a greater extent in apparatus used for the refrigerating drying of gases whereby moisture is to be drawn off from a surrounding gas such as compressed air. There are particular difficulties where the pressure thaw point lies below 0.degree. C. since then hoarfrost or ice forms on the components provided for dehumidifying. At low temperatures which are produced by cold brine or the refrigerant of a cooling assembly, this hoarfrost or ice attaches itself to the surfaces designed specifically for this purpose. After a greater or lesser length of service life this covering becomes so thick that it has to be removed for economy reasons or in order to maintain the efficiency of the apparatus.
An apparatus for the refrigerating drying of gases of the kind mentioned at the beginning is known from DE-A 39 41 713 whereby the removal of the ice crystals is carried out by heat shocks by means of electro impulses, by pressure shocks, for example by means of ultrasound, or by thawing processes. These are relatively expensive measures wherein in the case of thawing there are still the additional problems described in connection with the air-conditioning systems.
It is an object of the invention is to provide an apparatus for the refrigerating drying of gases wherein de-icing can be carried out in a simple way without interrupting the refrigerant production operation.